[Erythema nodosum: 112 cases. Epidemiology, clinical aspects and histopathology].

In a retrospective study we analyzed the cases of 112 patients with erythema nodosum treated during the period 1983-1993 in the Department of Dermatology, University Hospital of Basel, Switzerland. The aim of the study was to investigate the epidemiology, incidence of different etiologies, relevance of laboratory investigations and the histopathologic features in our patients, 83% of whom were females. The peak incidence occurred between the ages of 18 and 34 years. The commonest cause of erythema nodosum was infection. Other etiologic factors were adverse drug reactions, sarcoidosis, Crohn's disease, non-Hodgkin lymphoma, pregnancy, discoid lupus erythematosus, Sharp syndrome and aspartame. Only 47% of patients showed the classic bilateral distribution of the nodes on the extensor surface of the lower extremities. 77% of infection-induced erythema nodosum healed after 7 weeks, the longest course being 18 weeks. In contrast, 30% of idiopathic erythema nodosum lasted more than 6 months. Patients in whom erythema nodosum was associated with non-Hodgkin lymphoma had an extremely protracted course. Erythema nodosum associated with non-Hodgkin lymphoma may precede the diagnosis of lymphoma by months. In 4 cases erythema nodosum was the initial sign of sarcoidosis. In 30% of biopsies we found single vessels with leukocytoclastic vasculitis. The histologic pattern failed to provide etiologic pointers.